Scanning electron microscopy (SEM) or electron probe microanalysis (EPMA) are micro-analytical techniques, which provide the ability to image or analyze materials that are typically non-observable with the resolution offered by visible techniques. The imaging capability allows for the photographing of an object much smaller than what can be seen even with the aid of an optical microscope, while the analyzing ability allows for the identification of the elements (e.g., silicon, iron, etc.) of which the specimen is composed.
Scanning electron microscopes have generally been used as cameras for photographing specimens beyond the capabilities of ordinary optical microscopes. While the images obtained appear very real and as if they were photographed by ordinary means, the apparent illumination is a function of particle emission rather than radiation. These emitted particles are termed secondary electrons (SE). Secondary electrons are produced within the specimen as a result of primary eBeam electrons interacting with weakly bonded electrons within the specimen. Secondary electrons are emitted from the surface and detected.
The detection of secondary electrons via a SE detector is displayed on a scanning TV display. A bright image is the result of high secondary electron emission, and the primary influence on SE emission is the surface structure of the specimen. The end result is therefore brightness associated with surface characteristics and an image that looks very much like a normally illuminated subject.
Scanning electron microscopes have been widely used for integrated circuits, which have increasingly small scales beyond the capability of optical microscopes. However, scanning electron microscopes have mainly been used for the imaging of surface structures, and few efforts have been concentrated on the research of viewing the characteristics of the integrated circuits related to the internal structures. Further explorations to extend the capability of scanning electron microscopes thus have become a necessity.